The present invention relates to a process for the preparation of a zeolitic type catalyst with high stability in its physical, chemical and catalytic properties to obtain high octane gasoline by the conversion of paraffinic and naphthenic hydrocarbons present in the feed to a naphtha reforming process.
More particularly, this invention relates to a procedure for the preparation of a monometallic platinum catalyst on an inorganic oxide/zeolite support, preferably beta zeolite, used to convert paraffinic and naphthenic hydrocarbons which are present in the naphtha reforming process.
There exists a great variety of naphtha reforming catalyst which comprise a support to which metals from Group VIII are integrated by simultaneous or stagewise impregnation methods or by using incipient wetness techniques. The support may be a synthetic or natural inorganic oxide or a combination of both, such as alumina, alumina-silicate, magnesium oxide, bentonite, diatomaceous earth, silica, crystalline zeolites, and others. However, reforming processes are generally carried out in the presence of low cracking catalysts which limits the acidity range. Therefore, the most common supports used for the preparation of these catalyst are alumina, especially high purity alumina (gamma or eta alumina), magnesia, crystalline aluminosilicates (zeolites) with controlled acidity, or a combination thereof.
Metals from Group VIII (8, 9 and 10) which have been used are cobalt, nickel, ruthenium, rhodium, palladium, osmium, indium and/or platinum. Metals from Group IA which have been used are lithium, sodium, potassium, rubidium, cesium and/or francium.
U.S. Pat. No. 4,987,109, which patent is incorporated by reference in its entirety, discloses a procedure for the preparation of a high activity, selectivity and stability catalyst, using L type zeolite to which washings are performed using an aqueous potassium solution, with a 9.4 to 10 pH and integrating platinum to the support, using tetraamino platinum chloride as a platinum source.
U.S. Pat. No. 4,992,158, which patent is incorporated by reference in its entirety, discloses a procedure to prepare a catalyst for a reforming process. Such catalyst contains a noble metal in a faujasite or L type zeolite. Catalysts are prepared by treating zeolites with platinum or palladium acetilacetonate or both, or platinum sources such as tetraamino platinum chloride or chloral platinic acid in aqueous solution at 1 wt % concentrations.
U.S. Pat. No. 5,066,628, which patent is incorporated by reference in its entirety, discloses a procedure to obtain a bimetallic catalyst for a reforming process containing an L zeolite on which the cationic sites have been exchanged with potassium or barium or both and containing a noble metal and rhenium. This catalyst brings high selectivity to aromatics formation. The catalyst has a platinum/rhenium weight ratio between 0.01:1.0 to 10:0, which platinum is integrated to zeolite (BaKL) by incipient wetness impregnation with nitrate tetraamino platinum aqueous solution, and rhenium is integrated by incipient wetting with ammonium pherrenate aqueous solution.
The present invention involves a catalyst preparation technique which is relatively simple and provides a naphtha reforming catalyst having a high activity and stability in naphtha reforming including reactions of dehydrogenation, dehydrocyclization and naphthene and paraffinic isomerization, which results in high octane gasoline.
The present process involves a process for preparing a reforming catalyst which comprises incorporating a group IA alkali metal from an aqueous alkaline solution into a zeolitic material by means of ion exchange to form an alkali metal-modified zeolitic support material. The modified zeolitic support material is dried, calcined and combined with an inorganic oxide. The combined material is dried and calcined to form a stable inorganic oxide/zeolitic catalyst support. The inorganic oxide/zeolitic catalyst support is impregnated with a Group VIII metal to form an impregnated inorganic oxide/zeolitic catalyst support. The impregnated inorganic oxide/zeolitic catalyst support is dried, calcined and reduced to provide a naphtha reforming catalyst.
Surprisingly, the catalyst produced by the process of the present invention does not require a continuous chlorine adjustment to maintain the chlorine concentration as required by a commercial catalyst, as hereinafter demonstrated.
More specifically, the process involves the following stages:
1. Preparing the zeolitic material, modifying its intrinsic acidity by means of a neutralizing agent;
2. Drying the modified zeolitic material at a temperature to eliminate moisture, and calcining the dried product at high temperatures;
3. Preparing the support by combining an inorganic oxide and the modified zeolitic material with a chemical treatment, and further support preparation with the alumina and modified zeolite;
4. Drying the alumina and modified zeolite support to eliminate moisture and subsequent calcination at high temperature to generate stable physical and chemical properties in the support;
5. Preparing an impregnation solution with the desired metal in an alkaline media and contacting the solution with the porous support using ion exchange at room temperature to impregnate the support with the metal; and
6. Drying the support impregnated with the metal, calcining the impregnated support in an oxidizing atmosphere and activating the catalyst in a reducing atmosphere.
The resulting catalyst contains an element of Group IA (1) and an element from Group VIII (10) together on a refractory support of inorganic oxides with elements from Group IVA (14) and IIIA (13). To integrate the mentioned metals, an ion exchange method is used to integrate an element from Group IA (1) into the zeolitic material and the resultant zeolitic material is impregnated by incipient wetness or ion exchange (Group VIII (10) metal complexes) to integrate this metal into a cylindrical, spherical or trilob support which is formed with inorganic oxides from Groups IVA (14) and IIIA (13). These oxides are treated for stabilization and activation, giving place to a high activity, selectivity and stability catalyst.